I just had a quick question about watering. I’m using FFOF in a 5 gallon fabric pot. How much water should I be giving my plant
aloha, i call watering the most alchemic part of growing. 
watering your plant is not a constant like the whole growing process.
growing is a dynamic process or a journey where the environment and the plant goes through a lot of different stages. it took time, and, for me, also a lot of mistakes to find the right things to do at the right times at the right amounts. anyway it requires a lot of patience and commitment to succeed.
BUT
i grow in soil and try to water about the amount that lets the plant want more water in about 2 days. 3 is ok 4 days is my limit. and this makes around 5th or 6th of the pot volume. but this works for me my lights and my plants.
good luck
btw dont take my word since i am not the pro or the best grower in town 
5-10% of the volume of the container is a safe bet always. So being in 5 gallon you would probably want to start at 1/4 of a gallon to half gallon and adjust from there. I have had plants in 5 gallons that will drink a whole gallon of water a day…especially when you flip to flower. The age and size of the plants will also be a factor. Obviously lifting the pot when dry and wet will help tremendously in gauging when to water. Hope this helps and happy growing!! Feel free to reach out with any more questions 4 sure!
If you are using fabric pots, water till they it begins to seep from the lower sides of the pot, I usually go 2 days max as my lights are very hot and I use circulation fans, I usually end up using about 1 gallon per plant give or take a few ounces